This invention relates generally to geological measuring devices and more specifically to seismic measurements using arrays.
In many geological applications, including drilling and prospecting, seismic operations are frequently performed to generate and collect information indicative of the physical properties of subsurface formations. In addition, in many construction, drilling, and excavation applications, the knowledge of what is under the ground is necessary to avoid water mains, gas and electrical lines, foundations, and the like. A conventional seismic land operation includes placing a seismic cable along the surface of the earth. Usually, the cable extends in a straight line and contains many wire pairs. Seismic acquisition on land has in the past utilized a plurality of geophone arrays strung together by wire for the purpose of electrical communication to a multichannel recording unit. Individual geophone arrays normally consist of a plurality of geophones that are planted in survey lines spaced groupings of 12 to 24 geophones over distances of 55 to 440 feet by unskilled operators who often have little regard for proper orientation of the geophones.
In an attempt to improve data quality, three-dimensional geophones have been used to measure motion in three orthogonal directions. Each three-dimensional geophone typically includes three separate unidirectional geophones that are oriented for three-dimensional pickup and housed in a single enclosure, as typified by the geophone described in U.S. Pat. No. 5,010,221 entitled xe2x80x9cThree Dimensional Geophonexe2x80x9d which issued to McNeel on Apr. 23, 1991, and is incorporated by reference herein. These devices are disadvantageous in that they are difficult to repair and require strict horizontal placement.
In a typical seismic survey for a large geographical area, the area is traditionally covered by a plurality of survey lines. Seismic profiles are then recorded along each of the survey lines. The survey line is taken out after the profile is recorded and a new survey line is set up for recording the new profile. For the application of collecting data for three-dimensional imaging of the subsurface, it is necessary to record profiles from many survey lines in different positions.
On land, a seismic cable, typically approximately two miles in length and formed from a series of identical sections, is laid on the ground along a survey line. There is connected a two-wire conduit to electrically interconnect at each takeout or branch, for example, about thirty geophones into a single group or array. Each geophone group is located in the general vicinity of the takeout of the seismic cable to which it is attached.
A sensor platform has been used before in which sensors are mounted directly to a rigid horizontal frame described in U.S. Pat. No. 5,221,122 entitled xe2x80x9cSensor Platform for Use in Seismic Reflection Surveysxe2x80x9d which issued to Sansone on Jul. 27, 1963, and is incorporated by reference herein. This device is intended for use in marine and fast moving river applications.
Furthermore, in the past, software and other methods used to calculate the seismic data have been designed for operators who have extensive training in interpretation of such data. These methods suffer from the time and energy of placing sensors in survey lines. These methods have the inherent problems of if the line is not place correctly, it will affect the quality of the data acquisition. It takes operators with a great deal of training to properly set survey lines to collect three-dimensional data. In addition, each time a survey line is disassembled, there is a great deal of wear and tear that the sensors experience, thus leading to a shorter lifetime of these sensors. Moreover, the collection of data using these methods requires a highly trained specialist to interpret the data in order to generate three-dimensional images.
In accordance with the present invention, the preferred embodiment of a seismic sensor array includes a sheet of material and seismic sensors mounted to the sheet. In a further aspect of the present invention, the array includes devices, such as a rigid frame, vehicle mount or trailer, to make the seismic sensor array portable and transportable. In another aspect of the present invention, the seismic sensor array is part of a seismic measurement recording system which includes a data collection box and a computer. The computer includes software that produces three-dimensional images of seismic data that is collected in real time. A method of use of the present invention includes the positioning of the array, and collecting and processing data.
The seismic sensor array of the present invention is advantageous over the conventional devices in that the present invention array is lightweight, portable, and can be used in many different environments. The array keeps the sensors fixed and consistent allowing for a real time data processing system to be built. The data processing system reduces set up and processing time thus allowing the collected data to be viewed in a three-dimensional format in a matter of seconds. The present invention is also operable by operators with minimal training. Furthermore, contractors, excavators, utility repair teams, environmental consultants, and geologist can use the present invention a minimal amount of training. Additionally, in the present invention, the seismic sensors are mounted to a sheet of material that is easily moveable and eliminates additional wear and tear on the sensors from being taken out of ground after each survey line is disassembled. Additional advantages and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.